The present invention relates to a stand for optical equipment and, more particularly, to a stand having a movable support arm for optical equipment used in the examination of a patient's eyes.
During a typical eye examination, a physician will often use optical accessories which must be accurately aligned with the patient's eyes and which are generally relatively heavy such that a support structure must be provided to support the accessory. The accessory may be in the form of a device which carries a plurality of lenses to aid the examining physician in determining the corrective eyeglass lenses required for the patient. The device is typically aligned with both of the patient's eyes and thus the support structure must provide for movement in a vertical direction, a horizontal direction toward and away from the patient and in a direction which allows a plane of the device containing the lenses to be aligned perpendicular to the patient's line of sight.
The support structure for mounting the accessory is typically in the form of an elongated arm which is mounted to a vertical support post. Counterbalancing means such as a tension spring is often provided to bias the arm upwardly and thereby counterbalance the weight of the accessory. Further, the arm may be constructed with a parallelogram structure which pivots in a vertical plane about an axis located adjacent to the post such that the angular relationship between the accessory and the post will remain constant as the arm structure is pivoted in a vertical direction.
In addition to the above-described pivoting motion of the arm, the support structures of prior art devices have also included means for permitting the arm to pivot about the vertical axis of the support post and for permitting the accessory to pivot about a vertical axis located adjacent to the end of the arm distal from the post and thereby provide pivoting movement about three separate axes.
In order to lock the accessory in a desired position relative to a patient, prior art devices have included a pair of adjustment knobs wherein a first knob is located adjacent to the support post for locking the support arm against pivotal movement about the axis of the post, and a second knob is provided adjacent to the end of the arm distal from the post for both locking the arm against vertical movement and for locking the accessory against pivotal movement about the axis at the distal end of the arm.
Thus, the person adjusting the position of the accessory must alternate between locking the two adjusting knobs until the accessory is finally locked into the desired position relative to the patient's eyes. This arrangement has proven to be inconvenient since movement of the accessory about one of the vertical axes will usually necessitate a corresponding movement about the other vertical axis such that both of the locking knobs must be manipulated.
Accordingly, there is a need for a counterbalanced optical support arm which allows an accessory to be manipulated about three separate axes and in which the arm may be simultaneously locked against movement about all three axes by a single easily manipulated mechanism.